diff --git a/sphinx/builders/manpage.py b/sphinx/builders/manpage.py
index 532d2b8fe..897b310cf 100644
--- a/sphinx/builders/manpage.py
+++ b/sphinx/builders/manpage.py
@@ -65,7 +65,7 @@ class ManualPageBuilder(Builder):
             docname, name, description, authors, section = info
             if docname not in self.env.all_docs:
                 logger.warning(__('"man_pages" config value references unknown '
-                                  'document %s'), docname)
+                                   'document %s'), docname)
                 continue
             if isinstance(authors, str):
                 if authors:
@@ -79,8 +79,8 @@ class ManualPageBuilder(Builder):
             docsettings.section = section
 
             if self.config.man_make_section_directory:
-                ensuredir(path.join(self.outdir, str(section)))
-                targetname = '%s/%s.%s' % (section, name, section)
+                ensuredir(path.join(self.outdir, 'man' + str(section)))
+                targetname = 'man%s/%s.%s' % (section, name, section)
             else:
                 targetname = '%s.%s' % (name, section)
 
